Treatment of gas



Patented Oct 16, 1934 UNITED STATES TREATMENT OF GAB .Waclaw vonPiotrowski and Josef Winkler, Drohobycz, Poland No Drawing. ApplicationAugust 30, 1933, Serial No. 687,514. In Poland November 12, 1932 9Claims.

This invention relates to the treatment of town gas as is used forilluminating and other purposes. More particularly the invention relatesto an improved method of preventing the deposition of solids in gasmains, meters, etc., whereby the expense heretofore involved inmaintaining a gas-supply system fully operative-at all times,

is materially reduced.

It is well known that one of the disadvantages l0 occurring mostfrequently in cold weather is the deposition of solids in gas mainswhereby they become clogged. Coal gas contains naphthalene vapors whichhave a high vapor tension, and when the temperature of the gas fallsbelow the dew-point for naphthalene, solid naphthalene is depositedgenerally at diflicultly accessible or narrow passages in the gas mains.

Numerous attempts have been made to remedy this situation as by washingthe gas with oils which dissolve naphthalene quite readily. This methodis not satisfactory because it does not remove all of the traces ofnaphthalene which may be deposited. More recently naphthalene solvents,such as tetralin, have been injected into the gas, and upon cooling ofthe gases the solvent is deposited in liquid form and containing thenaphthalene dissolved therein. This liquid condensate is drawn off bysiphons without interrupting the operation of the system.

A. solvent which .is suitable for this purpose must have a high solventpower for naphthalene even at low temperatures. The vapor tension of thesolvent must be great enough for it to be suilicient for completesolution of the naphtha- 36 lene, but it must not be too great asotherwise the cold gas will contain too large an amount of solventdissolved in vaporous state, with the result that a larger quantity ofsolvent is necessary. The solvent must be insoluble in water 40 and haveno corrosive action on the gas mains,

meters, etc. It must be also completely combustible and its combustionproducts must neither be disagreeable nor detrimental. Finally thesolvent should be as cheap as possible.

As stated above, it has been proposed to employ tetralin(tetra-hydronaphthalene). It has also been proposed to employ xylol andits homologues, but these are even more expensive than tetralin.

It is an object of the present invention to provide an improved methodof preventing deposition of solids in gas mains, particularly to preventthe deposition oi naphthalene, and to pro- .vide a more economicalmethod than has hitherto been possible.

It has now been observed that the oxidation or dehydrogenation productsobtained by oxidation of mineral oils form very cheap and highlyefiicient solvents for the naphthalene contained in coal gas. Thecomposition of these solvents varies in accordance with the extent ofthe oxidation, the nature of the raw material and other factors. Thesynthesis of these products forms no part of the present invention. Itis sufiicient to observe that these solvents maybe readily and cheaplysecured in known manner by the oxidation of hydrocarbon fractions eitherunder pressure in the liquid phase, as is shown in the Penniman BritishPatents Nos. 255,020 and 256,922, and in the Burwell U. S. Patents Nos.1,690,769 and. 1,770,875, or by oxidation in the vapor phase with orwithout the use of catalysts as has been described by Ellis 8; James.

The raw materialsused in these processes may be petroleum fractions,crude petroleum or petroleum residues, shale oils, tars and asphalts,wood distillation oils, 'etc. These oxidized dehydrogenated productshave found use in various arts as, for example, in denaturing alcohol.Similarly other oxygenated hydrocarbons obtained from acetone oils,furfurohturpentine, and the compounds resulting in the catalyticconversion of water gas may also be used.

All of these products comprise high boiling point mixtures consisting ofaromatic compounds, unsaturated compounds and high-molecular neutraloxygenated compounds. The proportions of each of these three broadclasses of constituents may vary considerably, but in most cases verycheap and highly eilicient solventsfor the naphthalene contained in coalgas are secured. Compared, for instance, with the priceof tetralin,these mixtures may be obtained at one-fifth of the expense.

It should be observed that mineral oil hydrocarbons per se are notsuitable for dissolving the naphthalene, while furthermore the solventsemployed in accordance with the present invention have a far greatersolvent capacity for the naphthalene than is possessed by acorresponding amount of tetralin.

In practicing the invention the non-corrosive combustible solvent whichpreferably hasa boiling point of between 150 and 250 C., and which maycontain high molecular neutral oxygenated organic compounds, is injectedinto the gas, and upon cooling of the gas it is deposited and ex tractsfrom the gas all of the naphthalene which would be deposited in solidform in the gas mains. The solvent in liquid form is removable from 110the gas mains by siphons without interfering with the operation of thegas supply system. As is indicated, the oils obtainable by oxidation ofpetroleum, are very suitable for the purposes of this 5 invention, andit will be appreciated that so long as all of the naphthalene whichwould separate,

below the dew-point therefor is 'efliciently removed, it is notnecessary for attempts to be made to remove any remaining naphthalenewhich may still exist in the gas in vapor state and which will not bedeposited at the lowest temperature to which the gas may be subjected.In the winter time the temperature in gas mains may be as low as C. orlower. So long as there is present in the gas mixture in vapor form asufficient :Iecting oxygenated non-corrosive hydrocarbon oils into thegas and then vaporizing and condensing said oils.

5. The method of removing that portion of naphthalene contained in coalgas which is deposited at temperatures below the dew point for thenaphthalene, which comprises the dissolution of the excess naphthalenein an oxygenated non-corrosive oil mixture having a vapor tensionsufliciently great to retain the naphthalene in solution uponcondensation, but low enough to avoid excess vaporization of said oilmixture in the gas stream, and subsequently separating out the oil.

6. The method of preventing clogging of gas mains in use which comprisesinjecting into the gas stream a non-corrosive combustible solvent fornaphthalene, having a boiling point of between about 150 and 250 C. andcontaining dehydrogenated non-corrosive hydrocarbon .oils possessinghigh solvent power for naphthalene and relatively low vapor tension, andthereafter with- B011!!! Solvent 11mm:

Va r pressure in mxn. Hg.

For a gas which contains 130 m naphthalene per in at Solution of thenaphthalone wt. percent 20 following are necessary At 2? O. 2? 10" 0 C.

INS-210 a 17 mm. 105

1300 g. per 1000 m The amounts secreted are not sufllcient (ordissolving the naphthalenesecreted.

0. H) mm. 750 g. per 1000 m As may be seen from the above table, theoxidized hydrocarbon oils have a far higher solvent capacity than hastetralin, and hence less quantitles of it are required in the eilicientoperation of the process.

It will be appreciated that numerous variations will readily suggestthemselves to those skilled in the art without departing from the spiritand scope of this invention as set forth in the appended claims.

We claim:

1. The method of preventing deposition of naphthalene in gas mains whichcomprises incorporting in the gas a non-corrosive liquid combustiblesolvent for naphthalene boiling between 150 and 250 C. and containinghigh-molecular neutral oxygenated organic compounds and thereafterremoving said solvent.

2. The method of preventing deposition of naphthalene in gas mains whichcomprises in- .jecting non-corrosive oils obtainable by oxidation ofcrude petroleum oils into the gas, and thereafter removing said oils.

The method of preventing deposition of naphthalene in gas mains whichcomprises injecting into the gas, oxygenated non-corrosive hydrocarbonoils, and then separating the gas and oils.

4. The method of preventing deposition of naphthalene in gas mains,which comprises indrawing the solvent containing the dissolvednaphthalene from the gas stream.

7. The method of preventing deposition of solids in gas mains whichcomprises introducing a substantially non-corrosive but combustiblemixture of aromatic, saturated and unsaturated and highmolecularoxygenated organic compounds, having a boiling point of between 150 and250 0., into contact with the gas, cooling the gas to condense themixture and withdrawing the mixture from the gas stream.

8. The method of preventing naphthalene deposition in gas mains whichcomprises mingling the gas with a volatile non-corrosive solvent fornaphthalene, and thereafter cooling the gaseous mixture to condense saidsolvent and removing it from the gas stream, said solvent containingsuch liquid fractions as are obtainable by the dehydrogenation of crudepetroleum, petroleum distil- 13 lates, shale oils, petroleum residues,tars, and asphalts.

9. The method of preventing deposition of naphthalene-containing solidsin gas v mains which comprises removing excess naphthalene from the gasby subjecting the gas while still hot to the solvent action of oxidizednon-corrosive mineral oil, cooling the gas to condense said oil,

- and withdrawing the condensed oil from the gas.

JOSEF WINKLER.

WACLAW Von mo'mowsm.

